Case Study National Grid Deep Energy Retrofit Pilot Program Two-Family Belmont Residence Belmont, Massachusetts PrOject PrOfile Overview Project Team: Byggmeister,Inc, General Contractor; September 2010 saw the completion of the second project The DEAP Energy Group, DER participating in National Grid’s Deep Energy Retrofit (DER) Design Consultant; Building pilot program. This program provides financial incentives Science Corporation; National Grid, and technical support to residential retrofit projects that Massachusetts commit to achieving significant energy reduction. As the Technical Team in this pilot program, Building Science Location: Corporation (BSC) supports the projects by evaluating Belmont, Massachusetts and approving project plans, providing technical support, Description: and performing site visits for verification of measures and Comprehensive renovation of circa testing. BSC also supports the program by participating in 1925 two-family residence; 4,090 ft2 DER workshops. above-grade living space, 3-story residence with conditioned basement. This project involved an extensive interior and exterior renovation of an uninsulated two-family home built in Completion Date: 1925. The work involved for this retrofit was significant, September 2010 but it restored the original charm of the interior and Estimated Annual Energy Savings: exterior of the residence while at the same time Projected 74% energy use reduction dramatically reducing energy demands. Energy- compared to the pre-retrofit residence; saving improvements for the project included a super- with the addition of PV’s, expected to insulated enclosure, high performance windows, high meet Thousand Home Challenge efficiency heating and cooling, solar water heating, and mechanical ventilation. With support from the National Grid DER program, insulation levels were increased and the project was improved in many details with rigorous peer-review and supervision. The renovation plan included a conditioned shared basement, a finished third floor to be part of the upper unit, and upgrades throughout both units. Rev. 12/2011 © buildingscience.com National Grid Deep Energy Retrofit Pilot Program: Two-Family Belmont Residence 2 Builder PrOfile design Parametric study Of sOurce energy use Byggmeister is a design build firm in Newton, MA that was founded in 1983 and focuses on sustainable residential remodeling. The company mission includes environmental stewardship at the center of its services. The company is a business member of NESEA, Energy-Efficient Building Association and the Green Decade Coalition of Newton. On this project, Byggmeister worked with The DEAP Energy Group which specializes in energy modeling and consulting for Passive House, zero-net energy, Thousand Home Challenge, and other high-efficiency Image from BSC generated by NREL’s BEOpt 1.0 for retrofits building standards. The overall retrofit strategy for the it was included within the thermal ParticiPating PrOgrams & enclosure for this project was to literally enclosure. Closed-cell high-density certificatiOns wrap the above-grade portion of the spray foam insulation was applied to the house in a continuous and sealed layer interior side of the foundation walls and of insulation. As part of the National covered by a steel stud framed partition Grid DER pilot project, the goals for the wall with mineral wool insulation. thermal performance of the enclosure were R-40 for the exterior walls and R-60 The existing oil boiler steam heat system U.S. Department of Energy’s was replaced with a new energy efficient Building America Program for the roof. These targets were met by covering the existing board sheathing forced air system with heating and U.S. Environmental of the walls and roof with multiple layers cooling. The decision to change to forced Protection Agency of foil-faced polyisocyanurate insulating air required installation of ductwork for ENERGY STAR® sheathing and by blowing cellulose air distribution. This was not a major Program insulation into the previously uninsulated obstacle since much of the interior was wall and rafter bays. To accommodate being opened up for renovation. Also, the wrapping of the insulation from the as a two-family building, ductwork for wall to the roof, the existing rafter tails the lower unit could be primarily in the were sawed off. New eave and rake basement while ductwork for the upper overhangs were built and attached to the unit could be added as the attic was building structure through the insulating being finished. sheathing. All windows were replaced The air sealing target for National Grid with triple glazed windows located in the DER projects is 0.1 cfm at 50 Pascals outer plane of the retrofit wall assembly. (cfm50) per ft2 of enclosure which With exposed stone foundation walls, corresponds to 750 cfm50 for this project. the existing basement was cold, damp, As a result of installing a continuous and was subject to minor flooding. A air barrier system over the outside of sub-slab interior perimeter drainage the building and carefully detailing the system connected to a sump pump was air sealing of all penetrations, seams, installed for water management. Since edges and joints, the final blower door Deep Energy Retrofit Pilot Program the basement was to contain mechanical test measured air leakage of 590 cfm50, For more information, go to equipment and some finished space, exceeding the target by 20%. www.powerofaction.com/der National Grid Deep Energy Retrofit Pilot Program: Two-Family Belmont Residence 3 enclOsure design uRoof Assembly: Compact 1 (unvented) roof assembly with existing 7” deep rafter bays filled with netted cellulose insulation and with three 2” layers of foil-faced polyisocyanurate exterior insulating 1 sheathing. vWall Assembly: Existing wall framing cavities filled with dry cellulose and two 2” layers of foil- faced polyisocyanurate exterior insulating sheathing. wWindow Specifications: New Paradigm triple-glazed, krypton/ argon blend, low-E vinyl windows; U=0.2, SHGC=0.25. 2 2 xInfiltration: Self-adhering membrane over existing roof sheathing provides air control in field of roof. The taped outer layer of insulating sheathing on the wall is the air control layer for the field of the walls. The roofing membrane 3 overlaps the exterior wall insulation to provide a continuous transition. Closed-cell spray foam provides the air control layer for the foundation 3 wall. The transition from the exterior wall air control to the foundation wall air control is through the mudsill with sealant applied between the exterior insulating sheathing and the 4 mudsill and the spray foam over the foundation wall extending up over the mudsill. yFoundation Assembly: Conditioned basement with 3” 4 closed-cell, high-density SPF 5 insulation applied directly to stone foundation walls covered by metal stud walls with rock wool insulation. Sub-slab perimeter drainage system was installed and connected to a new sump pump. A drainage mat was installed along the base of the foundation wall and down under the new section of slab to allow foundation walls to drain to the sub- 5 slab system. National Grid Deep Energy Retrofit Pilot Program: Two-Family Belmont Residence 4 mechanical design 1 2 uHeating and Cooling: For each unit, 96.7 AFUE sealed combustion natural gas furnace in conditioned space with AHRI-rated 14 SEER/12 EER coil installed and connected to outdoor AC unit. vVentilation: For each unit, Energy Recovery Ventilator installed with dedicated ductwork; outside supply ducted to common 3 4 space; inside exhaust taken from bathrooms. wSpace Conditioning Distribution: Entire distribution system within thermal enclosure: ductwork in basement for lower unit; ductwork in attic kneewall space and floors for upper unit. xDHW: Solar thermal with common 100 gal. tank and, for each unit, a 40 gal. electric backup tank. 5 6 yLighting: ENERGY STAR® CFL lighting. Appliances: ENERGY STAR® dishwasher, refrigerator and clothes washer. zSite Generated Power: 4.3 kW PV system cOnstructiOn at the walls, it shifted to the outer layer contractor was able to implement effective The builder and homeowner acknowledged of exterior insulating sheathing. While transition methods as confirmed by the the importance of air leakage control transitioning the air barrier from the roof final blower door test. for a successful deep energy retrofit by to the walls was fairly straightforward in As enclosure improvements are including an airtightness goal in their spite of the change in location of plane, made – thermal, air control, and water contract. It would do well for other projects details for the transition at the walls to management – the relative importance of to follow this example. the windows and to the mudsill at the basement was complicated by this choice. the window installation increases. Fully The enclosure design established the air To make these transitions simpler, BSC aware of this, the contractor and window control layer at the roof to be the membrane had recommended moving the wall air supplier scheduled a full scale mockup of applied over the existing sheathing (and control layer to the housewrap layer over a window installation at the site to verify under the exterior insulation) whereas the existing sheathing. However, the the details. National Grid Deep Energy Retrofit Pilot Program: Two-Family Belmont Residence 5 testing During the project, BSC visited the site to observe the implementation of the different measures included as incentives in the project. This included inspection of installed window details and of insulation before the exterior and interior finishes were applied. After the renovation was substantially complete, BSC measured ventilation rates within the individual units and mOving fOrward conducted guarded blower door testing to determine the overall air tightness of The DEAP Energy Group is continuing the building. The blower door test result to commission and monitor the operating of 590 cfm at 50 Pascals (cfm50) was conditions of the project now that the a dramatic improvement over the pre- residence is occupied. In addition, retrofit air blower door test result of 5700 agreements between National Grid cfm 50.